Method of producing synthetic fuel



April 5, 1949. w. E. SKELTN METHOD OF PRODUGNG SYNTHETIC FUEL 2Sheets-Sheet l Filed Aug. l0, 1944 April 5, 1949. w. E. sKELToNMETHODAOF PRODUCING SYNTHETIC FUEL Filed Aug. l0, 1944 2 Sheets-Sheet 2Patented Apr. 5, 1949 VWilliam E.-.Skelton, yBeacomll. X.,vassignor toA.The .Texas Company, .N .ew York,N. Y.,a .corporation .of DelawareApplication IAugust 10, 1944, Serial No. 548,870

s Claims. .1

.This :invention relates Lto the vmanufacture rof motor -fuel and jmoreparticularly aviation .ga-soline, and 'is particularly directed :to theproduction of high octane `aviation igascline -jof the type .classedV:as super-,fueL

It is conventional practice to prepare so-:called i100 .octane .aviation:gasoline by :blending @a .suitable .base stock, such .as .straight-run.orwcatalytireally. cracked :naphtha -of :high octane, Withvarious:synthetic :fuel components :or `additives such .as @C4 alkylate and:hydrogenated `polymer fgasoline, :together -.withisopentane .and:amanti-knock compound of thecharacter of .tetraethyl lead. Where.aviation gasoline of still .higher performance values is required, lasdetermined by .the 'fwe'll `known AFD-LC :and AFD-.3C vknock:ratingtests, Yit has 'been .necessary to include .larger proportions up tosubstantially 100% of the synthetic fuels, thereby reducing the:proportion :of `the ibase fuel permissible in the blend, and also.include `:aromatic additives of the .character off /cumene v.to improve:the .rich `mixture performance .in .supercharged engines 'as determinedby the AFD-.3C test. .It `has been vfound that lrisobut-aneethylenealkylate, prepared under certain critical f f xconditions with .an:aluminum lhalide acatalyst, produces a high yield 4.ofv2,3-diniethylbntane, which latter :has exceptional properties `iiormproving 'the vAFD-3C erich mixture .rating While at the Sametimeavoiding'the normal deterioration of the AFDelC rating `encountered with.the .aromatic additives vheretofore employed. 'While ythe total C2alkylate can .be :employed as :such :an .aviation gasoline :additivewith .good results, it is preferred to utilize a .fraction :boiling uptovabout 265 F., or even a yC5-C26 cut or a ,hexane `cut Which is highlyconcentrated in the fdesired2,3 fdimethylbutane.

One of the `chief diiiculties heretofore encountered in the ldesign .ofa plant to manufacture thesaid C2 alkylate additive A'as .a bomponent.of high grade aviation .gasoline tor super-fuel, has been lthe highinstallation and operating :expense involved in the preparation of Yasatisfactory ethylene .feed :stock .t or the C2 aalkylation unit. .It

:is .desirable that the lethylene feed stock .should contain vat leastabout A3.0% `by weight :of ethylene, Yand `preferably .about :4D-:50%,:and :should .be comparatively free from propylene .or .at least 'havenot lmore than .about 10% by wete-ht of ipropylene based on tthe yWeight-of the :ethylene in the charge. Also, :the feed stock should containless than .about 30%, and `prefer-ably.less than .25 by lWeight of lixed:gases .lighter Vthan G2, namely .methane and hydrogen. While .re-

.I2 iinery ,gases from fboth thermal Land `catalyticfcrac'leingoperartions `are vavailable in Alarge i quantities, the`ethylene -icontent of these vgases `is comparatively low, and theexpense of `low-.temperature :high-pressure fractionation to separatebetween -ethy-lene .and methane and .form a desired ethylene fchfa-rge:stock yhas been Econsidered eco- .nomicall y -vunattractive `with theequipment `and metho ds available.

.It has heretofore been Asuggested that Tan fethane-,propane .feedAstock be .thermal-1y convented under temperature and flow pressureconditions to ,pro-duce .-a .resultant fconversion ,productenrichedfinfethylene, which can be subsequently treated by fractionation.and selective polymerization .to yremove ipropylene, to thereby producefan ethylenecharge for the C2 alkylation .Thisfprocess involvesexpensivefractionation, and the Ca polymer .resulting from ,the selective.polymerization is .of llower grade, suitable for motor -iuel `ibut notyfor `high -g-rade 4aviation gasoline. :Even in -this case, the ethylenecharge is diluted 'with .a large Vproportion oi eth-ane, methane land:hydrogen and the'dilu'ent gases-in large proportion Irender the chargeAdiiiicult to handle in the C2 alkylationfstep, and result insubstantial .losses -of un-reactedethylene and ireduction 4in the 'yieldci the C2 alkylate. Y

@ne of :the principal `objects yof the present invention is to provide.la unitary process lfor producing Yaviation gasoline yor super-fuelincluding .C2 alky-Iate as a component thereof., `and wherein -a .puriedand concentrated ethylene yfeed stock izor the alkylationsteprisobtained 'as acomponent par-t of the `unitary process rand in a simpleand economical manner without having to fractionate lbetween ethyleneran-d methane.

lAnother object of the present invention is `-to provide -an improved.method of preparing 4a concentrated ethylene feed :stock by acombination xof ,petroleum oil cracking, thermal vconversion -of a C3.and lighter condensate fraction of the .selectively from gases llighterthan "C2, :and a rcracking gases `from the cracking step, anabsorptionfoperation-for treating'uncondensed products of -the thermalconversion vto 'absorb Cz of .catalytic Vcracking under conditions togive high gas yields and form `a :high .grade `aviation base stock,thermal conversion -of Ca :and lighter condensate gases from thecatalytic cracking, recovery of a purified and concentrated ethylenefeed stock low in fixed gas content from the products of thermalconversion, alkylation of the resultant ethylene feed stock to producethe 2,3- dimethylbutane additive, and catalytic conversion of C4constituents of the gases from catalytic cracking by alkylation orco-polymerization and hydrogenation or both, and blending of theresultant high grade products.

Another object of the invention is to provide an improved recovery andrecycling system for an aluminum chloride and HC1 alkylation unit,whereby both HCl and isobutane are recovered in substantial amount fromthe offgases in a simple and inexpensive manner for recycling to theunit.

A further object of the present invention is to provide an aviationsuper-fuel and an improved method of producing the same, including ablend of aviation base stock, C2 alkylate, hydrocodimer or mixtures ofhydrocodimer with C4 alkylate, and an anti-knock agent, such astetraethyl lead.

Other objects and advantages of the present invention will be apparentfrom the following description when taken in conjunction with theattached drawing and the appended claims.

As a preferred and specific embodiment, the process of the presentinvention involves catalytic cracking, particularly ilulid catalystcracking, of a suitable petroleum oil feed stock such as gas oil,depropanization of the resulting naphtha and lighter cracked hydrocarboncondensation products after removal of the tail gas, thermal conversionof the overhead from the depropanizing step to substantially increasethe ethylene content thereof while materially reducing the C3 content,compressing and refrigerating the compressed stream from thermalconversion to Yeffect partial condensation with separation ofuncondensed vapors from resulting condensate,

passing the uncondensed vapors in contact with a Cri-C4 absorption oilproduced in a subsequent step of the process to absorb most of theethylene and eifect a separation from methane and hydrogen, passing therich absorption oil together with the above-mentioned condensate to afractionating step where a Cz and lighter fraction containing atleast 30weight per cent of ethylene and less than 30 weight per cent of methaneand lighter is taken overhead and thus separated from a Ca-Ci bottoms,the major portion of the latter being returned to the absorption step toserve as the absorption oil, alkyiating the resulting C2 and lighterfraction with isobutane under conditions to produce a C2 alkylateconsisting mainly of 2,3-dimethylbutane, debutanizing the depropanizedproducts of catalytic cracking to separate a C4 fraction from astabilized cracked naphtha, subjecting the C4 fraction to catalyticalkylation and/or co-polymerization and hydrogenation to produce C4alkylate or hydrocodimer or preferably both, and blending an aviationfraction of the stabilized cracked naphtha with said C2 alkylate, saidC4 alkylate or hydrocodimer or preferably both, and with a suitableantiknock agent, such as tetraethyl lead, to produce a resultantaviation super-fuel.

The invention is more particularly illustrated in the attached drawingwhich shows a preferred embodiment thereof, and wherein Fig. 1 is adiagrammatic view of a portion of the apparatus for carrying out themethod of the present invention; and

Fig'. 2 is a continuation of Fig. 1 and is a dia- 4 grammatic view ofthe balance of the apparatus. Referring to Fig. 1 of the drawing, a gasoil charge stock is introduced by the line I0 to the heating coil II,where the temperature is raised to about E50-900 F. The heated oil thenpasses -by line I2 to the catalytic cracking unit I3, where 'it iscracked in the presence of a suitable active cracking catalyst, such asa synthetic silicaalumina. It is to be understood that any conventionaltype of catalytic cracking can be employed, such as xed bed, fluidcatalyst, etc., although fluid catalyst cracking is preferred. It willbe appreciated that the gases from catalytic cracking are moreunsaturated than the corresponding gases from thermal cracking, andcatalytic cracking is therefore preferred for the present process. Wherethe object is to produce a high grade aviation gasoline or super-fuel,the cracking step is carried out under more severe conditions to producehigher gas yields and proportionately lower motor fuel or naphthayields, thereby forming increased quantities of ethylene and C4 olefinswhich are subsequently converted to the high grade motor fuel additives.For this purpose, the fluid catalyst cracking is generally carried outat the higher temperatures of about 950-1000 F. and low pressures of theorder of 5-10 pounds gauge, with a severity factor determined by thecatalyst to oil ratio and the weight of oil per hour per weight ofcatalyst held up in the reactor to provide a conversion of (5U-80% ofthe gas oil charged, as is well understood in this art. This willproduce roughly about 15-25% by weight of total C4 of whichapproximately half is butylene, about 10-15% of C3 and lighter with theethylene running around one-third or more of the C2 content, and about3545% of 400 F. E. P. naphtha.

The resulting cracked products pass by line I4 to fractionator I5, wherecycle gas oil is removed as a side stream I6, and heavier material,together with remaining suspended catalyst, is removed as bottoms byline I'I leading to a suitable filter or thickener for the recovery ofthe catalyst in conventional manner. It will be understood that thefluid catalyst cracking unit is merely illustrated diagrammatically, andany suitable conventional unit can be employed for this step. Moreover,it will be appreciated that the heating coil II need not be provided,since the oil can be heated to the desired cracking temperature bydirect contact with the hot catalyst from the regenerator, as isconventional practice in certain of the iiuid catalyst cracking units.

The resulting cracked naphtha together with the crackingrv gases pass byline I8 to condenser and cooler I9 and thence to accumulator 20, Whereuncondensed gas passes 01T by line 2l. This gas is picked up bycompressor Illa and forced under high pressure of the order of 200pounds per square inch through line I la to a conventional absorptionand stripping unit indicated by I2a. Here the gas is cooled andcontacted with a suitable absorption oil, such as a 3438 gravity gasoil, to absorb a substantial proportion of the condensable gases.Unabsorbed gas, including a substantial proportion of the Vfixed gases,namely methane and hydrogen, and

termed tail gas, is discharged from the top of the absorber by line I3ato the refinery fuel lines. The rich absorption oil containing theabsorbed gases then passes to a stripper, Where the absorbed gases arestripped out of the remaining lean oil, which latter is then recycled tothe absorber after being cooled. The overhead gases :cracking ofjpropa-ne and propylena .are chilled and Icondonsed to -form ltheiso-called ""absorption condensate? which 51s returned lsto "the system"by pump Ma-and line 15a.

`While the tail gas of course contains vvsom-'e un- :condensed ethylene,it is found that vthis separation 'is highly desirable `'in order `toremove a large part of the methane and substantially .all Aof thehydrogen from the system. This iis limhportant-,since Athe and lighterfeed stock ultirnately supplied to the thermal conversion un'it shouldbefrelatively low vin inert or xed Jgases ('C1 and H2) and 'preferablyshould run below-'2.0 `volume1: erc'ent'of such -xed gases. Byut'ilizing only the gas condensate ifrom the cracking 'operation anddischarging the tail gas, expensive low tempera-ture fractionation toremove methane Iand hydrogen from the gas charge to the thermal4'cor-lversion is avoided, -thereby effecting fan `economical advantagein spite oi someloss `of ethylene in the tail gas.

The 'condensate from accumulator '218 iis then forced by pump 22athrough line l22, where it -is mixed with the absorption condensatefromv line 15a, -and the mixture passed into the prestabilizmovedoverhead by line v24. A portion of the overhead stream sucient forreflux is diverted by line '-25 through condenser 26 to accumulator v2l"and returned by pump 28 and line 29 to the 'top of tow-er 2-3. 'Thebalance of the voverhead gas which may be under line pressure of about-200 pounds 'per square inch at atemp'erature `of about 100 F. is passedthrough a pressure reducing valve Bill, where the pressure lis -loweredif necessary to provide an outlet pressure 'from the thermal conversioncoil `3`| of 0-50 pounds per square inch gauge. vIt will be vappreciatedthat 'the coil inlet pressure for this Vcondition will be dependent uponthe coil design and the Icharge rate. 'Thecharge -gas is heated to atemperature of about '1400" to eiect crackin-g in the coil, yandthe'cracked products are then rapidly cooled wlthoutallowing appreciablesoaking time to precent any substantial polymerization with theformation of normally liquid products.

Under the conditions specified above, 'the :charge gas fed to thethermal conversion unit will gene-rally `contain about-'304119 -byvivtngg'lfift of C2-*of which at least half is ethylene, about 40-55 lbyweight of C3, less than l@ weight per -cent of methane withsubstantially no hydrogen, and a small `percentage of C4. It lisVdesirable that this charge gas be as high in `ethylene content aspracticable, `since the yethylene appears fto A`pass `through thecracking coil substantially unchanged. Therefore, 'the vdepropanizeroverhead Afrom the catalytic cracking condensate represents 1a very'suitable charge stock 1.to the gas "conversion step, since it is higherin initial ethylene icontent than the Ycomparable vfCs and lighter'fr-action :obtained 'from the condensate `ol? `tl'ierxn-al cracking,and `is vmuch higher in ethylene :content vand much lower 1in methaneand hydrogen content than the C3 and lighter -gases from eitherv'catalytic yor thermal cracking vtrom. which the gas has not beenseparated. The propane-propylene ratio of the charge gas appears:relatively unimportant, since :both of these constituents are:susceptible to cracking 'to ethylene iequa-l degree. Some :ofthe ethaneof the .charge Igas .of :course breaks down with the lcnrnalti-on of.ethylene and lighter; but *additional ethan-eis v,formed fin the .gasconversion istep .from -the Conso' vquently, the .ethane content of ltheproducts of --zstant'ally decrease the Cs content :of the charge `gas,while at the same tune increasing the ethyllfenfe, methane, and hydrogen:content thereof with .little ior no increase .of the fethane content.Also, there :is fa very smallbLuld-up to 'C4 and heavier. The:ineuiftablebreakdown to Vmethane and :hydrogen under these conditionsis not objectionable since the :charge :gas .had :been 4lair-,relydenuded of .these yconstituents and the resultant products of`conversion will therefore :contain `.less than about 25% by Weight ofmethane and hydrogen. .This proportion fof the lighter or `i'ixed :gasescan readily be tolerated in the subse quent absorption step `withoutobjectionable .loss of ethylene. Such isinot the lcase where the xed gascontent of the products of conversion is higher, :since the :sweepingieffect -of higher :proportions of these Li'lxed gases acts to entrainethylene in the olegas from Ithe absorption :step with @correspondingly.greater `loss of the vdesirable ethylene.

lThe conversion products from :cracking @coil 23:1 4are passed by line.32 to exchanger 33 `icontaining heating coil M connected `to wasterheat bo'ler r35. 'Boiler feed water :is supplied by line fsand passesvthrough :the vneat exchange coi-l 2311, whereby the waste heat of theconversion prodfuchs is `used to generate high pressure steam, such assteam tof :150 `,pounds per isqua-re linch gauge, :and the conversion:products are `llherc'eby "rapidly cooled below Aa reaction temperature.The -resulting :gaseous products of thermal :.converson, whichana-y`thereby ;be cooled from 1400" to around 4660 `thencefrpass by .line 3l`.through Water cooler 3B Where Athey :are vfurther @cooled to about110" The gases .are ythen lfed 4byline 39 :to :a compressorlw, wherethey are compressed to about #500 pounds per-:square inch, and thenceare supplied to 'exchanger 41 where they are refrigerated to yabout 0"F. with refrigerant supiplied 'byjlirrefl iatabiout -20 The resultantcompressed Vand refrigerated kproductszare `then introduced by vline 4.3into accumulator 44,` where vapor-liquid `separation .is rinade. Thiscondensa.- :tion substantially .reduces `the load on the abfsorber fand'materially improves the :ethylene rre- .covery in the :absorptionrstep.

'The :llncorndensed'zzgases from accumulator 44 pass -by :overheadvaporline 45 to absorber Mi, which latter .is supplied `with la leanabsorption `oil `by line 41.. Asfwi-llrbe more particularly describedhereinafter, the Vabsorption .oil :is Aprefer-ably `-a Csech'bottoms:obtained,fromme-conversion prodnots, land -therefore'supplied by thesys-tern. yThe heat ol' absorption is continuously removed-laycirculating condensate from fan `intermediate tray of the fa'bsorber'byline l48 through 'exch-anger '49 supplied with refrigerant atabout-20"Fr-.byli-ne 59 and :returned loy'guump 5| :and line -52 rizo a 'flow'ertrayI fofl the absorber. `By fthe use lof this 75, tweenthe ethylenefand-:ethane on l:tlie @one hand;

.ntercoole1:, the tempera,ture :of 'the ,absorbergis end Lmetlume.undvhydrogen .on Ythe othen whereby -a substantial proportion of the methaneand most of the hydrogen can be removed by overhead lline 54 throughpressure release valve 55 as tail gas which can be sent to the gas fuellines. The net result is a recovery of a C2 and lighter product gas inthe absorber containing about 40 weight per cent of ethylene for anoverall recovery of about 94% of the ethylene in the gas supplied to theabsorber by line 45. By somewhat reducing the percentage of overallethylene recovery down to say '85%, a product gas will be absorbedcontaining as high as 50 weight per cent or more of ethylene in the C2and lighter portion.

The rich absorption oil passes from absorber 46 by bottom line 51 and ismixed with a stream of condensate passing from the bottom of accumulator44 by line 58. The mixed stream then flows through pressure reducingvalve 59 where the pressure is reduced to about 400 pounds per squareinch, and is introduced into fractionator 62, and to which high pressuresteam is supplied from the waste heat boiler 35 by line 63 and branchline 64.

The C2 and lighter overhead from fractionator 60 passes by line 65through exchanger 66 supplied with refrigerant at about 20 F. by line61, the chilled overhead then flowing by line 68 to accumulator 69 wheresuflicient liquid is .condensed to supply vthe reiiux requirements oftower 60, said reux being returned to the tower by pump 10 and line 1|.

Lean oil accumulating in the bottom of fractionator 60, and whichconsists essentially of Cri-C4 hydrocarbons with the C3 amounting to atleast about 80% by weight thereof, is discharged by line 12. A majorproportion thereof is recirculated by pump 13- and line 14 through watercooler 15 and then through exchanger 16 supplied with refrigerant atabout F. by line 11, and the refrigerated lean oil then passes by line41 to the top of the absorber to serve as the absorption oil therein; Itis thus seen that the bottoms heavier than C2 from the gas conversionunit 3| is utilizadas the absorption oil, so that absorption oil from anextraneous source is not required. Moreover, sufiicient makeup Ca-Ci iscontinuously formed and supplied from the conversion unit 3|, so thatthe absorption oil in the system is continuously replenished, while someexcess is continuously discharged from the system. This excess howsthrough line 18, and all or any portion thereof may be recycled by line19 to the inlet of the conversion coil 3| for recracking.

Since the high temperature employed in the rconversion unit 3| producesa small amount of aromatics, a portion ofthe excess bottoms iscontinuously or intermittently diverted by line 80 'through heater 8|,where the temperature is' raised to about 40G-500 F. The heated (J3-C4.

'..polymerized to form Vpolymergasoline for motor fuel. Products ofpolymerization are passed by line 83 to depropanizer 84, where C3 andany lighter is removed overhead and returned by line 85 to the recycleline 19 for return of this material to the thermal conversion unit 3|.In this manner, heavier aromatics are removed from theabsorption-stripping system to prevent build-up therein, while at thesame time a yield of polymer gasoline for motor fuel is obtained andunpoly merized paraiiin gases recovered and recycled to the thermalconversion unit. Thedepropanized polymer gasoline is discharged fromtower 04 by line 86 leading to a suitable stabilizer and thence tostorage (not shown).

Uncondensed C2 and lighter is removed from accumulator 69 by line 81together with any excess condensate over that required as reiiux fortower 60 and which is removed by liquid line 88. The resultingconcentrated and purified ethylene charge then passes through pressurereducirlar valve 89, where the pressure is reduced to about Z50-300pounds per square inch as desired for passage through the C2 alkylationunit hereinafter described. The charge then passes by line 90 throughproduct heater 9| supplied with high pressure steam from waste heatboiler 35 by line 63 and branch line 92 to compensate for the heat ofexpansion and to raise the temperature of the charge to about 1l0-130 F.The puriiied ethylene charge at the proper pressure and temperature thenpasses by line 93 to the C2 alkylation unit as more particularlydescribed in connection with Fig. 2.

Referring again to the depropanizer 23, the catalytically crackednaphtha bottoms from that tower is passed by line 95 to the debutanizer96 which is operated to remove C4 overhead by line 91. The stabilizedcracked naphtha then passes by line 98 to the fractionator 99 where thedesired aviation fraction is removed overhead by line |00 throughcondenser |0| to accumulator |02. Aviation naphtha base stock is thendrawn from this accumulator and passed by line |03 to theblending tankfor the preparation of finished l aviation gasoline, as moreparticularly described hereinafter in connection with Fig. 2. The heavynaphtha bottoms from fractionator 99 are withdrawn by line |04 tostorage for motor fuel.

The overhead C4 fraction from line 91, which contains a high proportionof butylenes in addition to isobutane and normal butane, is passed allor in part by line |05 to the C4 alkylation unit |06, where thebutylenes are alkylated in conventional manner with isobutane introducedby line |01 in the presence of a suitable alkylation catalyst,preferably strong sulfuric acid or hydrouoric acid, introduced by line|08. As the conditions for butylene alkylation are well-known and anyconventional type of alkylation unit, such as the pump and time tank,jet reactor or impeller reactor, together with customary neutralizing,washing and fractionating equipment, can be employed, no furtherdescription of this step is required. A debutanized 311 to 350 F. endpoint fraction of the C4 alkylate is passed by line |09 to the blendingtank described in connection with Fig. 2.

On the other hand, all or any part of the C?. fraction from line 91 maybe passed by branch line 0 to the C4 copolymerization unit l I, whereisobutylene and normal butylene are copolymerized in conventional andwell-known manner. The resulting codimer or fraction thereof boiling upto about 265 F. is then passed by line ||2 to a hydrogenation unit ||3to saturate the product and form hydrocodimer inconyentional manner'.The resulting hydroc'dinnis fsuppliediby l'in ll'l to the blending tankdescribed in connectioniwith Fig. 2.

The proportions 'of fthe 'Ci :faeti'on from `1ine'9'l supplied to C4alkylation and to hydro'odimer production `respectively depend upon theAi'solii-'1t'alle and butylene balance of the particular refinery aswell as up'on the ultimate grade `o"f iai/lation gasoline desired.Botnthe ci -lkylation andthe C4 alk'ylati'on :require substantial'amounts Adf "iso-'- butan'e. Where the is'obutane s'upply is limiting,and there is an 'oversilpply of butyl'en'es fin relai tion to isohutaneyrequired 'for `Ci alkylation and C4 alkyl'ation, then a part o'i fallof the Ci-niy She passed to hydrooo'diifnfer production, with .povi sionfor the recovery of 'the isbutane in the charge supplied thereto by linerijn, so that this isobtane 'can b'e used forCg aflikylaitoh. lVV-heftethere vis a plentiful supply :of isobutane `"and ma# oapacity of'aviatiohalkylate fis desi-riedjthn' all or Substantially Aall 'f theC11 frein VYliie 9-1 Will be passed to C4 alkylatio'n. However, wherethe object is to produce a high grade "s'uioe'i'i-ieli, A'and qualityrather than 'quantity 'of the aviation :glas-1 olih'e is controlling,the' G4 charge 'will generally be split between the el alkyl'ation unitand the hydrocodimer unit to v'provide b 'o'th types 'of high gradeaviation oripoilet's 'foi' blending Withvth C2 alkyl-ate and the caaiyti'cally cracked base stok in the manner her after dsiibed.-

Refeir'gfto Fig; l2, 't e pil e'd 'd trated ethylene hae fro ii'lle 93passs" by line IIS together with fresh feed isobutane from line IIT andrecyolei'sob'uitah'e from l-iln'e 'I'BM'tthe surge tank |'|9.FiOln-iir'eytn una 'ie' passs byline lat and either of Vvalve controlled'tranen lines |2| and |22 to one bf a' pair b'f de u ation tanks |23andl |24. These tanks nlleu with activated aljiiiiiiinabr other dita-bledehydiatin' agent which "serves 'to' m'dv i ture from the hydrocarbon balkylaton unit. The d'hyia il e` flows by either of brauen lines '|25'and |26 line rzl, which in tui-fiy cbnnebts with lin-ej |29 leading toth alkylati ate'r-l l tanks I 23 and |24 are operated'alt being on-St'lea'in for' drying? the4 h', e Whil" other is being fea-buvait 'i sir'supplied' by line- |30 containing steainbe |31 and connected by vali/e'ebntijollci bib elles |32 andv l|33` with tanks '|23 and |14 r by eitherof branch-lines |34 "nu ls'etb line |36 containing water c'oler |31, andl'adin to water settler |331. Water ieiiibved freni tneiclsliyurj j ingbed by the ratjj ating? gas is separated from that gas in las anduisbliarg'uby line |39V to suitable disposal, while the' rea V thenpassed hy line |40 to asil'itablholder? f ultimate retu'ln to line |'3'0and rertlfilla'i'ilig i`n theV system.

The C2 alllylation reactor |42i ispreff" the tower type as desorifbedand-elairnefd' ln pending application of Louis Clarke,v Se 535,261, filed'May 142;'- 1`94l5; new Pali 2,.1.C|",137YV dated September 3;lgllywttfil: tions of' the reaction as described application. Forexample; weer 14a may be is feet in diameter and 7 0 vfeet' in" heightand lly nearly toe the top withV a alu4 sin hydrocarbon-commend ti' eddition-ofd'ispersd aluminum hlonde: Th co ples liquidi may be' "pared-byneati""g herbs e,

napbtna. or alkyl @blends steli teit being mainly etnan-e andriii-etnane. and u ii'gfV i ene' tlijeenarg' gas can' butyl chloride;with aluminum `c hlrid'e until liquid p'rcidl'lct -is r4formed as the-result 'of fafcoml binatin vkoi' complexing of the 'aluminum chloridewith the hydrocarbon o'r alkyl chloride; Ker# serr isfgenrally used -toinitially form'the co'mpleii liquid for 'starting lip `the plant, andthereafter the' ndessary `makeup vooinplex 'liquid -is .supplied ih'si-til. by Taon b f al-kyla-te with dispersed aluminum 'chloride To thepreformed complet liquid there is added a quantity of anhydrous aluminum4chloride which 'is dispersed in 'the 'coniplei: liquid and aiotiyat'esthe same. Duringr conitinuacef the Aprocess; additional aluminumchloride is added :by line |43 to maintain the aci tivity of thecatalyst; as generally controlled by measurement of "rthe heat vofhydrolysis which shuld be maintained above about r320 Calories per graniAv activated Complex' liquid.

activated aluminum chlorideehydrocaboh complex liquid is maintained asthe oontinuo'us phase in the tower and -the isobutarie-ethylen'e chargetogether with a smallproportion `of HC1 in"V` trod'uce'd by line' IMA inva, pro'portio'n' t .provide less than 0;1% lby .Weight on the Weight-(if the hydroearbon charge; are passed through line' FM and dispersedthrough a plurality of nozzles or orifices fl i5 into the liquid`catalyst body adjt'loe'nt the base of the tower. As 'heretoforedescribed, the `pressure -n the tower is maintained at around 225 poundsper square inch so that the isobltan', which is usedy substantialv'molar excess "of the ethylene', 'is liquid "phase: ethylene feedhowever may be in gas phase, being effectively rise upwardly through thecatalyst liquid dueto dilrere'no'fe in gravity therebetween and withoutsufdient agitation' to-v frm anv e'rnul's n; until they reach the upp'rsurface thereof, when the Y liquid hydrocarbon constituents' o'alsce" tfrny alsupsrpbseu'hydrocarbon layer attire top '6i tli tower;

witnanfetnyiertnarge gassosi-aiding atleast abut :3o weight vper centetnyiene-,` the b" with "ai suitable absorption oil;` suh as a" 36:538"soil, byline |55'. The absorber -i"s"'cnoled by recirculation fromintermediate' tray th'" iirlflflinev |57 passing'throgh Watercooler |58an t ned-by line- |59 to* Icwe tr y. Th'

ets ana'- of the iso'butane from the gas, which latter is` discharged byoverhead line |60 to fuel, or may be recycled to the inlet of theconversion heater 3| as illustrated in Fig. 1. It will be understoodthat the above described recovery and recycling process is generallyapplicable to any isoparaiin alkylation process employing aluminumchloride and HC1 as the catalyst, and particularly a mixed phase processwhere both HC1 and isobutane are present in oigases from the alkylationunit.

The enriched absorption oil passes by line |62 through steam heater |63into the upper portion of stripper |64. Live steam is introduced intothe bottom of the stripper by line |65 and serves to strip out theabsorbed isobutane. The lean absorption oil is returned from the `bottomof the stripper by pump |66 through Water cooler |61 and thence by line|56 to the absorber |55. Overhead vapors of water and isobutane passfrom stripper |64 by line |68 through water cooled condenserl 69 toseparator |10, where separate layers of condensed Water and isobutaneform. The lower Water layer is discharged to ditch by line |1|. Theupper isobutane layer is returned by line |12, pump |13 and line ||8 toform a portion of the recycle isobutane for the C2 alkylation unit. Asthis recycle isobutane is mixed with the ethylene charge in advance of,the dehydration unit, any remaining water is thereby effectivelyremoved.

When it is desired to recover the HCl in the off-gas of line |50 forrecycling to the aikylation unit, an alternative procedure is employedin scrubber |5|. In place of supplying an alkaline solution to thescrubber by line |52, a constant boiling mixture of water and HC1 issubstituted,

containing approximately 11 mol per cent HCl and 89 mol per cent H2O.Contact of this constant boiling mixture with the vapors in scrubber |5|dissolves or absorbs the HC1. HC1 solution discharged by bottom line |53is then passed by line |50a to a distillation tower |5|a containing aclosed coil heater |52a. The excess HCl is removed overhead by line 53a,dried in a suitable sulfuric acid or alumina drier |54a, and recycled byline |55a to line |44. Theconstant boiling mixture of HCl andwater-.dis-m charged as bottoms by line |56a from the distillation unitis passed through a suitable cooler |`51a and then recycled by line |58aand line |52 to the scrubber |5|. Depending upon the percentage of HC1employed' in the hydrocarbon charge to the alkylation unit, the expenseof recovering and recycling the HCl may be less than the expense of thefresh HCl and neutralizingagent required in the first describedprocedure, in'which event the HC1 recovery system is used. Ordinarily,where proportions of HCl less than about 0.05% by weight of thehydrocarbon charge are employed, the HC1 recovery system is noteconomically justied and the neutralization procedure is used.

The hydrocarbon liquid layer in gas separator |49, in which some of thecomplex catalyst-may beentrained, passes by line |15 to settler |16Where the liquid complex catalyst immediately drops out and is returnedby gravity through line |'|1,to the continuous catalyst phase withintower-v |42. Excess complex liquid formed in situ in the tower |42during continuance of the process is discharged intermittently orcontinuously at a low rate by bottom line |18. This also serves toprevent the thickening or increase in viscosity of. the complex liquidwhich would otherwise occur during long periods of continuous operation,

The enriched.

` liquid by line thereof is diverted to line |8| through water cooler|82, and thence recycled by line |41 and pump |83 for mixing with thefresh hydrocarbon charge from line |21 and recycle isobutane from line|46, the mixture passing through line |28 to the :dispersion nozzles |45in the base of tower |42 as `previously described. This hydrocarbonrecycle :thus serves to maintain the proper reaction temperature withinthe alkylation tower, as well asv to supply a substantial volume ofliquid for mixing with the gas phase of the hydrocarbon charge, therebyproducing more eiective dispersion and reaction of the ethylene in themixed phase operation. A minor proportion of the hydrocarbon productfrom line |80 is discharged by line |85 to the deisobutanizer |86equipped with reboiler |81 and operated under conditions to. removeoverhead an isobutane-rich stream containing up to 95% or more ofisobutane. This isobutane stream passes through condenser |88 and line|89 to accumulator |80, from which pump |9| returns a portion thereofthrough line |82 to serve as reflux for the tower, the balance beingrecycled by line |46 to the alkylation charge line |28 as heretoforedescribed.

-line |99 to accumulator 200, from which pump `through a heating coil201 where the temperature is raised to about 300 to 650 F. andpreferably about 500 F. The heated alkylate then flows by line 208through either of valve controlled branch lines 209 and 2|0 into one ofthe clay treating chambers 2| and 2|2. These chambers are filled with asuitable percolation clay, such as fullers earth, which serves to removecombined chlorine from the heated alkylate. This chloride removalmaterially improves the lead susceptibility and other desirableproperties of the alkylate.

VThe resulting chloride-free alkylate then passes by one of valvecontrolled branch lines 2|3 and' 2|4 to line 2 I5, which latterintroduces the same into alkylate fractionator 2|6. The percolation-clay chambers are employed alternately, so that jdimethylbutanemay runabout 'Z5-85 volume pery aie-casas cent, with the 4C5 content :being.less than 5 fvnhnne per cent, and the 'Cn-eCs content running about10-,15 volume per cent. The bottoms 'boiling above 265 F. Awill also:generally Irun vless Athan about 5 volume lper cent. Consequently, thedebutanized 265 F. end point ial-kylate fraction constitutes a verysatisfactory aviation tfuel additive to provide the rich mixture`performance and other desirable characteristics of .2,3-dimethylbutane.If desired, the cut point yon the fractionator 2 I S can be at the.initial boiling point of the C7 fraction to take overhead a Gis-CsInaterial; and the .latter can be further fractionated to separate atotal hexane cut or a material consisting almost entirely of2,3-dimethylbutane.

.The overhead aviation cut from fractionator 216 passes throughcondenser '2.18 and line 219 to accumulator 220 from which lpump 22|returns a portion as reflux to 'tower 216 by line '222. The bottoms fromtower 2|6 are passed .by pump 223 through cooler 224 and line 225 tostorage for motor fuel.

The desired proportion of the aviation fraction of the C2 alkylate isywithdrawn from :accumulator 220 by pump 226 and passed by line 221 toblending tank 228. Suitable proportions of .the C4 alkylate,catalytically cracked base stock 'andA hydrocodimer, produced asdescribed in connection with Fig. 1,'may also be introduced into theblending tank 228 by lines |09, H13 and H4 re spectively. In some cases,a high octane straight run aviation naphtha introduced by line 229 maybe used in conjunction with or in substitution for the catalyticallycracked base stock. In addition, the desired amount of anti-knock agentsuch as tetraethyl lead may be added by line 230, and commercialisopentane may be added by line 231. The resulting blended aviationvgasoline is discharged by line 232 to suitable storage. It will beunderstood that the aviation base stock, either catalytically cracked orstraight run, orcertain selected fractions thereof, lcan be acid treatedor subjected to catalytic rerunning in conventional manner prior tointroduction vinto, blending tank 228. It will also be understood that agum inhibitor may be added to the blend, particularly one made from thecatalytically cracked base stock; and any other agents, such as dyes,color stabilizers, etc. included in well known manner.

The following specific example is given as illustratory of the presentinvention, but it is to be understood that the invention is not limitedthereto.

A 81.7 gravity paraffinic gas oil having a 50% evaporated point at 675F. was subjected to :fluid catalyst cracking with a syntheticsilica-alumina cracking catalyst, resulting in a 65% conversion underthe following conditions:

Temperature, F. 975 Pressure pounds per square inch gauge 5-10Catalyst/oil weight ratio 4.5 'Weight of oil per hour per weight, ofcatalyst held up in reactor 1.0

The conversion products resulting from this operationv analyzed asfollows, based on the gas oil charged:

Per cent vCa and. lighter dry gas weight-- 11.05. Coke dok3.0

i Total C4 volume 2.2.0. C54O0 F. end point naphtha do- 40rd Cycle gasoil do- 35.0v

The depropanizer overhead 'resulting from de- 14 propanization rot' :thecombined cataitytlcally cracked naphtha condensateiand :the absorptioncondensate in depropanizer 23 (Fig. 1.), andsupplied as feed stock tothe gas conversion unit '31.; has the following typical analysis:

A typical analysis of ythe vconversion @products e from unit 3|,obtained with the feed `'seit fo'xf'th immediately above, is the.tollowingz Weight per cent Hydrogen 0.5 Methane 21.9 Ethylene 30.0Ethane 26.6 Propylene 9.0 Propane 7.3 C4 plus 4.7

With an overall recovery of 94% of the ethylene in theabsorber-fractionator system I6-60, the product gas supplied by line 93to the C2 alkylation unit analyzes as follows:

Weight per cent Hydrogen 0.2 Methane 21.9 Ethylene 41.5 Ethane 35.9 C30.5

The following tabulation is a -summaryofthe utilities requiredfor'producing 110,000 pounds of ethylene per stream day:

Fuel

Power Btn/nf.

. KWB/Hr.

Heater Gas Compressor.`

W a s t e H e a t Boiler C r a c k e d G a s Cooler Refrigeration.. vPumping, Reboiler Product Heater-.-

Net Total..

The 8,060 pounds of steam per hour enclosed in parenthesis in the abovetable represents a. net production in the waste heat` boiler 35,whichsubstantially supplies the steam requirements of the plant, leaving onlya net total of 520 pounds per hour to be furnished from an exteriorsource. The fuel requirements are readily met by the tail gas and othergases discharged to the fuelflines. TheV major requirement for coolingwater is readily obtained at low cost, and' they actualrefrigerationrequirements are low. It is therefore seen that the operating expense ofthe present method is extremely low in comparison with the utilitiesrequired for conventional low-temperature high-pressure fractionation,anda' very economical system is thereby presented.

The conditions of the C2 alkylationoperation and the results obtained,utilizing the concejo-1 15 trated and purified ethylene charge gas setforth above, are listed in the following table:

based on total hydr o c a r b o n charge minimum Alkylate yield weightper cent :ethylene reacted 262 Ethylene reacted, weight per cent ofethylene charged 81 ene mol ratio in thereactor, with a 67 volume percent`conversion to codimer based on the butylenes converted, and with a93% total butylene conversion. The polymerization products werefractionated to separate a codimer fraction boiling up to about 270 F.This fraction was then hydrogenated in the hydrogenation unit l I3 inconventional manner in the presence of Raney nickel at a temperature ofabout 450 F. and a pressure of about 1000 pounds per square inch tosaturate the codimer and produce the so-called hydrocodimer. y

Typical tests on the resulting C2 alkylate, C4 alkylate, hydrocodimerand the catalytically cracked base stock produced as described above,together with the same tests on a straight run aviation base stock`supplied from an exterior source, are set forth `in the followingtable:

C; alkylate C atayt- Smigh o approxi- C Ik 1 H M ica y t mately 75% 4 ay ycracked run base aa-dimethyt a comme has@ stock butano stock Gr., API81.0 70.0 66. 4 54. 3 62. 0 RVP, p. s. i 7.6 3.0 2. 7 6. 5 6.7 ASTMDistillation:

Init 132 160 169 114 110 137 190 220 134 144 144 222 23D 213 195 197 250238 311 238 273 319 265 340 305 Allrylate composition: Per cent byvolume 3 On the basis of 1000 barrels per stream day of alkylate, theisobutane and ethylene requirements are:

Isobutane consumed in alkylation reaction BPSD-- 730 Ethylene charged toreactor lbs./SD 109,830 Ethylene consumed lbs/SD-- 88,962

The C4 olenic feed charged by line |05 to the C4 alkylation unit 106 wasalkylated under conventional conditions in a pump and time tank reactorat a temperature of around 50 F., utilizing a 5/1 isobutane to butylenefeed ratio, a 150/1 isobutane to olen contact ratio in the reactor dueto emulsion recycle, a 60% isobutane concentration in the reacted mix, acontact time of minutes, a pressure -of about 50 pounds to maintain thereactants in liquid phase, and makeup fresh feed .of sulfuric acid of98% strength to maintain a titratable acidity within the reactor systemof about B9-9.0% HzSOfl.l The resulting alkylation products wereneutralized, washed, and fractionated in conventional manner, and a 310F. end point aviation alkylate fraction separated.

The portion of the C4 feed supplied by line I I0 to the C4copolymerization unit lli was treated under conventional conditions at atemperature of about :S20-345 F. in the presence of a xed bed phosphoricacid catalyst, utilizing recycle to maintain about a 2: 1 normalbutylene. to isobutylwhich is classed as a superfuel.

The invention is further illustrated in the following table showingtypical blends of the stocks listed above, together with commercialisopentane, to produce a 150 grade aviation fuel, The 12C/150 refers toArmy and Navy performance numbers, the 120 performance number being a 1Crating of isooctane plus 0.69 ml. TEL per gallon or a 1C index number of106; and the performance number of being a 3C rating equivalent to Sreference fuel 3.55 m1. TEL/gal. or a 3C index number of 152. The tableis based on the preparation of 100 barrels of this grade of aviationfuel containing 4 cc, TEL/gal.

.The aviation base stock set forth in the above table can be either thecatalytically cracked base stock or the straight run base stock listedin the preceding table, since the properties of the two base stocks aresimilar except for 3C octane and the proportions used are small, withthe result that little diierence occurs in the calculations for theabove blends with either base stock. The above table demonstrates thatthe smallest isobutane requirement for the production of this superfuelis in the blend of C2 alkylate with hydrocodimer. The largest isobutanerequirement is in the blend of C2 alkylate and C4 alkylate, but in thiscase arhigher proportion of. the base stock :agradecer is permissible.Consequently, where isobutane is available, while isopentane is limited,this represents a desirable blend. For maximum production of this gradeof aviationfuel with a relatively small but intermediate isobutanerequirement and a minimum amount of Cz alkylate, the blend containingboth C4 alkylate and hydrocodimer with the C2 alkylate is preferred.

It is obvious that various grades of aviation super-fuel can be producedby the method of the present invention, the above examples being merelyillustratory. Furthermore, while certain specific temperature andpressure conditions have been set forth above for the C3 and lighterthermal conversion, it is to be understood that these conditions can bevaried from the specifiedA preferred operating conditions. For example,temperatures of about 1250 to 1500 F. lcan be employed with pressuresranging from about atmospheric up to about 500 pounds per square inch orsomewhat higher. Also the specified conditions for the absorption andstripping operations for recovering the ethylene feed stock to the C2alkylation unit are merely the Vpreferred conditions for economicaloperation, and the temperature and pressure conditions can be variedfrom those shown and coordinated to give similar results as will be wellunderstood in this art.

While an activated aluminum chloride-hydrocarbon complex catalyst hasbeen described above as being preferred for the C2 alkylation, it is tobe understood that other aluminum halide catalysts can be employed forthis purpose. For example, other aluminum halide, such as aluminumbromide, complex liquids activated by the addition of aluminum halidemay be used. Likewise, a fixed bed operation with lump aluminumchloride, or a bed of inert contact'material impregnated with aluminumhalide may be employed. Likewise, in the C4 alkylation, while sulfuricacid or hydrofluoric acid are preferred as catalysts, other wellknowncatalysts for this reaction can be used, such as BFa-water complex,chlorosulfonic acid and the like. The copolymer can also be producedwith other conventional catalysts such as sulfuric acid, phosphoric acidand the like, as is well understood; and the hydrogenation ofthecopolymer can be carried out in well-known manner with otherconventional hydrogenation catalysts including metal sulfides andoxides.

As set forth above, condensate from catalytic cracking is preferredbecause of the higher olenic content. Moreover, catalytic cracking iscapable of producing a high grade aviation base stock, which is not thecase with the naphtha produced by thermal cracking. However, whereasuicient supply of high grade straight run aviation base stock isavailable, thermal cracking condensate including absorption condensate,from which tail gas has been separated, can be utilized as a, part orall of the charge to the thermal conversion unit in accordance with thepresent invention. In such case the thermal conversion may be carriedout under somewhat more severe conditionsl to increase the ethylenecontent, and the absorption step is generally operated with a lower netethylene recovery so as to effect the desired separation of methane andhydrogen and obtain a Cz charge for alkylation which is suflicientlyconcentrated in ethylene. The present invention thus .enables suchthermal crackingV condensate to be utilized as a charge for the processwith somewhat lower alkylate yield on the basis of the gas condensatehandled. This is feasible for a refinery which is not provided withcatalytic cracking facilities but hasa suilicient supply of crackedgases from thermal conversion operations and also a source of supply ofstraight run aviation base stock.

Further, it is to be understood that a portion of thermal crackingcondensate can be mixed with catalytic cracking condensate for purposesof the present invention. This is particularly suitable in those caseswhere the catalytic cracking produces an excess of aviation base stockover the required amount of C2 and C4 alkylates as well as hydrocodimer.By mixing a portion of the thermal cracking condensates with thecatalytic cracking condensate, the supply of ethylene and butylenes canbe increased to provide a renery balance, and thus utilize the productsproduced by 'the present process to the best advantage in the productionof maximum quantities of the aviation superfuel.

Obviously many modifications and variations .of the invention, ashereinbefore set forth, may Nbe made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim:

1. The method in the manufacture of high octane aviation gasoline whichcomprises recovering from the products of cracking of hydrocarbon oil aC4 fraction containing butylenes and a v.C3 and lighter condensatefraction containing a Vsubstantial proportion ofethylene and somemethane, subjecting the said C3 and lighter condensate fraction tothermal conversion at high temperature and low pressure to substantiallyin- 3,5crease the ethylene content thereof while ma- `terially reducingthe C3 content, recovering from the products of thermal conversion bycondensation and absorption most of the ethylene content of saidIconversion products in a refrigerated con- 40T,densate, fractionatingsaid last-mentioned condensate at a pressure substantially below thatrequired to fractionate between ethylene and methane to separate a C2and lighter fraction containing at least 30% by volume of ethylene andv,less than 25% by volume of methane and hydrogen, alkylating isobutanewith ethylene ofthe said C2 and lighter fraction in the presence of analuminum halide catalyst under alkylating conditions to produce a C2alkylate consisting mainly of 2,3-dimethyl-butane, dividing said C4fraction into two portions, subjecting one portion of said C4 fractionto polymerization and hydrogenation to form hydrocodilmer from thebutylene content thereof, alkylating isobutane with the other portion ofsaid C4 fraction in the presence of an acid alkylation catalyst toproduce C4 alkylate, and blending an aviation base stock with said Czalkylate, said hydrocodimer, said C4 alkylate and isopentane to formhigh octane aviation gasoline.

2. The method in the recovery from the products of cracking ofhydrocarbon oil of a fraction lighter than C3 containing a highproportion of ethylene, which comprises subjecting the crackedhydrocarbon oil products to cooling and condensation to form acondensate consisting of cracked naphtha together with lighter normallygaseous hydrocarbons, separating uncondensed normally gaseoushydrocarbons from said condensate, subjecting said separate normallygaseous hydrocarn bons to absorption with an absorption oil to absorb aportion of the said gases while the remainder passes off as tail gas,stripping the rich absorption oil to remove the absorbed normallygaseous hydrocarbons and cooling the latter to recover an absorptioncondensate, combining the nrst -mentionedcracked naphtha condensate withsaid absorption condensate from which tail gas has been separated,depropanizing said combined condensates to separate a C3 and lighterfraction containing a substantial proportion of ethylene and somemethane, subjecting said C3 and lighter fraction to thermal conversionat high temperature and W pressure to substantially increase theethylene content thereof While materially reducing the C3 content,cooling and compressing the products of said thermal conversion and thenrefrigerating the compressed products to effect partial condensationthereof, separating uncondensed vapors from the resulting condensate,passing the uncondensed vapors in contact with a Ca--CJt absorption oilproduced in a subsequent step of the process to absorb most of theethylene and separate the same from unabsorbed methane and hydrogen,passing the rich absorption oil together with last-mentioned condensateto a fractionating zone, separating a Cri-C4 bottoms from saidfractionating zone, refrigerating and recycling at least a portion ofsaid C3-C4 bottoms to the absorption step to serve as the aforesaidabsorption oil therein, and recovering as an overhead from saidfractionating zone a C2 and lighter fraction containing at least 30% byvolume of ethylene and less than 30% by volume of methane and hydrogen.

3. The method according to claim 2, wherein said C3C4 bottoms from thefractionating zone is divided, a minor proportion thereof being passedto a polymerization zone, depropanizing the resulting products ofpolymerization to separate a polymer bottoms containing the aromaticcontent from a C3 and lighter overhead fraction, and recycling the saidCx and lighter overhead fraction to thefthermal conversion step.

4. The method in the recovery of a hydrocarbon fraction lighter than C3Whichis enriched in ethylene from cracked hydrocarbon gas condensate,which comprises separating a C3 and lighter fraction containing asubstantial proportion of ethylene and some methane from saidcondensate, subjecting said Ca and lighter fraction to thermalconversion at high temperature and 10W pressure to substantiallyincrease the ethylene content thereof while materially reducing the C3content, subjecting the products of thermal conversion to compressionand refrigeration to eiect partial condensation thereof, separatinguncondensed vapors from the resulting condensate, passing theuncondensed vapors in contact with a Cs-C4 absorption oil produced in asubsequent step of the process to absorb most of the ethylene andseparate from unabsorbed methane and hydrogen, passing the richabsorption oil together with the last-mentioned condensate to afractionating zone, recovering a Ca-Ci bottoms from said fractionatingzone, refrigerating and recycling at least a portion of said Cs-Cibottoms to the absorption step to serve as the aforesaid absorption oiltherein, and separating overhead from said fractionating zone a C2 andlighter fraction containing at least 30% by volume of ethylene and lessthan 30% by volume of methane and hydrogen.

5. The method according to claim 4, wherein the said C3-C4 bottoms fromthe fractionating zone is divided, a minor proportion being passed to apolymerization step, depropanizing the poly- Inerization products toseparate a polymer bottoms containing the aromatic content of saidCa-C-i feed to the polymerization step to thereby prevent aromaticbuildup in the absorption system, also separating from saiddepropanizing step an overhead C3 and lighter fraction, and recyclingsaid overhead C3 and lighter fraction to the thermal conversion step.

6. The method in the recovery of a C2 and lighter fraction enriched inethylene from a C3 and lighter fraction of cracked gas condensate, whichcomprises subjecting the said C3 and lighter fraction containing asubstantial proportion of ethylene and some methane to thermalconversion at high temperature and low pressure to substantiallyincrease the ethylene content thereof While materially reducing the Cscontent, compressing and refrigerating the products of thermalconversion to eect partial condensation thereof, subjecting remaininguncondensed vapors to absorption in a light absorption oil produced in asubsequent step of the process to absorb most of the ethylene thereofand separate from uny`absorbed methane and hydrogen, combining theresulting rich absorption oil with the condensate from said partialcondensation step, subjecting the mixture to fractionation to remove aC2 and lighter fraction enriched in ethylene overhead, and refrigeratingand recycling a Cs and heavier bottoms from said fractionating step tothe said absorption step to serve as the aforesaid absorption oiltherein,

7. In the catalytic alkylation of isobutane with methylene to produce anaviation blending alkylate ,wenriched in ethylene and containing lessthan 2G volume per cent of methane and lighter, subjecting said Cs andlighter absorption condensate to thermal conversion at high temperatureand low pressure to substantially increase the ethylene xcontent thereofwhile materially reducing the C3 content, cooling and compressing theproducts of said thermal conversion and then refrigerating thecompressed products to effect partial condensation thereof, separatinguncondensed vapors from the resulting condensate, passing theuncondensed vapors in contact with a C3 and heavier absorption oilproduced in a subsequent step of the process to absorb most of theethylene and separate the same from unabsorbed methane and zhydrogen,combining the resultant rich absorption oil with said last-mentionedcondensate, passing the resultant combined mixture to a, fractionatingzone, separating a C3 and heavier bottoms from said fractionating zone,refrigerating .and recycling at least a portion of said C3 and Atherefor.

8. The method in the manufacture of high octane aviation gasoline whichcomprises recovering from the products of cracking of hydrocarbon oil a,separate C4 fraction containing butylenes. and a separate Csk andlighter` condensate fraction containing substantial proportions each ofpropane, propylene,v ethane and ethylene, and some methane, subjectingthe said C3 and lighter condensate fraction to thermal conversion athigh temperature and low pressure to substantially increase the ethylenecontent thereof while materially reducing the C3 content, recovering bycondensation and absorption most of the ethylene content of saidconversion products in a refrigerated condensate, fractionating saidlast mentioned condensate at a pressure substantially below thatrequired to fractionate between ethylene and methane to separate a C2and lighter fraction containing in excess of 30% by volume of ethyleneand less than 25% by volume of methane and lighter, alkylating isobutanewith ethylene of the said C2 and lighter fraction to produce a C2alkylate consisting mainly of 2,3-dimethyl butane, converting thebutylenes of said C4 fraction to high octane saturated parainichydrocarbons Within the aviation gasoline boiling range, and blendingsaid C2 alkylate and said C4 high octane gasoline hydrocarbons with anaviation base stock and isopentane to produce the said high octaneaviation gasoline.

WILLIAM E. SKELTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,421,733 Snelling July 4, 19222,154,676 Haeuber et al 1- Apr. 18, 1939 2,181,640 Deanesly NOV. 28,1939 2,226,467 Hjerpe et a1 Dec. 24, 1940 2,298,383 Ipatiei Oct. 13,1942 2,307,773 Eglog Jan. 12, 1943 2,309,986 Ruthruff Feb. 2, 19432,330,206 Dryer et al Sept. .28, 1943 2,340,600 Lamb et al Feb. 1, 19442,360,222 Roetheli Oct. 17, 1944 2,360,585 Ross Oct. 17, 1944 2,361,054Pevere Oct. 24, 1944 2,385,123 Atkins Sept. 18, 1945 2,389,231 Blumer1.--- Nov. 20, 1945 2,398,908 Miller Apr. 23, 1946 2,412,645 Munday Dec.17, 1946 OTHER REFERENCES Oil and Gas Journal, Mar. 19, 1942, pages 18and 19.

Certificate of Correction Patent No. 2,466,334.

April 5, 1949. WILLIAM E. SKELTON It is hereby certified that errorsappear in the printed specification of the `above numbered patentrequiring correction as follows:

Column 5, lines 43 and 44, for "preoent read prevent, column 15, hnes 34 5 and 6, strike out Reactor temperature, F 4/1 eactor pressure poundsper square inch i 110 so utane/olein mol ratio 275 and insert insteadthe follo Isobatane/olfyn mol ratio l4/1 r Reactor temperature, "F 110Reactor pressure pounds per square zack 275 column 16, line 47, for 3.55m1." read +3.55 ml.; and that the said Letters Patent should be readwith these corrections therein that the same may conform to the recordof the case in the Patent Office. Signed and sealed this 20th day ofSeptember, A. D. 1949.

